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An X‐ray diffraction study of the cross‐circulated canine heart.
Author(s) -
Matsubara I,
Suga H,
Yagi N
Publication year - 1977
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1977.sp011954
Subject(s) - diastole , cardiac cycle , systole , intensity (physics) , diffraction , phase (matter) , papillary muscle , materials science , medicine , cardiology , anatomy , physics , optics , blood pressure , quantum mechanics
1. The equatorial X‐ray diffraction pattern was recorded from a papillary muscle of a cross‐circulated canine heart at different phases of the cardiac cycle. The intensity ratio of the 1, 0 and the 1, 1 reflexions (I1, o/I1,1) was 0‐79 in the systolic phase and 1‐19 in the diastolic phase. 2. Using the intensity ratio obtained, the approximate proportion of the myosin projections present in the vicinity of the thin filaments was calculated. This was 70‐71% in the systolic phase and 51‐52% in the diastolic phase of the total myosin projections. 3. The peak systolic tension was roughly proportional to the proportion of the projections present in the vicinity of the thin filaments during systole. 4. The projections which stayed in the vicinity of the thin filaments during diastole did not produce significant contractile force.